Which of the following back pressure gauges is NOT used in Pneumatic Comparators?

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RRB JE CBT 2 (Mechanical Engineering) ReExam Official Paper (Held On: 04 Jun, 2025)

Answer 1

Explanation:

Pneumatic Comparators

Pneumatic comparators are precision instruments used to measure dimensions and detect variations in mechanical components. They employ the principle of compressed air to detect changes in dimensions by measuring back pressure. Back pressure gauges are key components in pneumatic comparators and are used to display the variations in pressure caused by dimensional differences in a workpiece. Various types of back pressure gauges are utilized depending on the application, but not all types are suitable for use in pneumatic comparators.

Absolute Back Pressure Gauge:

Absolute back pressure gauges measure pressure relative to a perfect vacuum, rather than atmospheric pressure. These gauges are used in applications where precise measurement of absolute pressure is required, such as in vacuum systems or specialized research environments. However, in pneumatic comparators, the emphasis is on measuring relative pressure variations caused by dimensional differences in the workpiece. The use of an absolute back pressure gauge in this context is unnecessary and impractical, as pneumatic comparators rely on relative pressure changes rather than absolute pressure values. Therefore, an absolute back pressure gauge is not used in pneumatic comparators.

Additional InformationVenturi Back Pressure Gauge

Venturi back pressure gauges work on the principle of the Venturi effect, where fluid velocity increases as it passes through a constricted section of a pipe, causing a corresponding drop in pressure. These gauges are widely used in pneumatic comparators to measure small changes in back pressure caused by dimensional variations. The Venturi principle provides high sensitivity and precision, making this type of gauge suitable for pneumatic comparator applications.

Water Column Back Pressure Gauge

Water column back pressure gauges measure pressure based on the height of a water column displaced by the applied pressure. These gauges are simple and reliable, making them suitable for use in pneumatic comparators. They are particularly useful for low-pressure measurements and offer an easy-to-read visual representation of pressure variations. Their use in pneumatic comparators is common, especially in basic or manual setups.

Differential Back Pressure Gauge

Differential back pressure gauges measure the difference between two pressure points. They are highly effective in pneumatic comparators, where the objective is to detect small variations in pressure caused by dimensional differences in the workpiece. These gauges provide accurate and reliable readings, making them an integral part of many pneumatic comparator systems.